Lubricant for metalworking

ABSTRACT

AN EMULSION LUBRICANT FOR USE IN COLD-ROLLING OF METALS CONTAINING, ON A WATER-FREE BASIS, FROM ABOUT 20% TO ABOUT 50% OF AN ORGANIC ACID, IS IMPROVED WITH RESPECT TO ITS HARD WATER STABILITY BY HAVING IN THE LUBRICANT AN AMOUNT OF A MIXTURE OF MONO- AND DIOLEYL PHOSPHATES.

United States Patent 3,723,314 LUBRICANT FOR METALWORKING Robert H.Davis, Pitman, N.J., assignor to Mobil Oil Corporation N0 Drawing. FiledMar. 24, 1971, Ser. No. 127,764 Int. Cl. C10m 1/06, 1/46 US. Cl. 252-3349 Claims ABSTRACT OF THE DISCLOSURE An emulsion lubricant for use incold-rolling of metals containing, on a water-free basis, from about 20%to about 50% of an organic acid, is improved with respect to its hardwater stability by having in the lubricant an amount of a mixture ofmonoand dioleyl phosphates.

CROSS-REFERENCE TO 'RELATED APPLICATIONS The subject matter of thisapplication is related to that of an application filed of even dateherewith in the name of Michael C. Churn, entitled Lubricant Useful inMetalworking. The mentioned related application concerns an improvementin metal working lubricants similar to those of this invention, theimprovement comprising the use of an aromatic oil. The application isSer. No. 127,763, filed Mar. 24, 1971.

BACKGROUND OF THE INVENTION Field of the invention This inventionrelates to emulsifiable lubricants useful in the cold-rolling of metals.More particularly, the invention is concerned with such lubricants whichhave improved hard water stability properties.

Description of the prior art The most modern rolling procedurespresently used to produce extremely thin gauge metal or strip productshave increased the burden on the roll lubricants. The overridingnecessity of obtaining increasingly higher gauge reduction per roll passand at even faster rates than used in the past has increased thestandard loadcarrying and cooling requirements of roll oils even moreso. Present commercial lubricants cannot perform adequately in thecold-rolling of steel, for example, wherein gauge reduction of over 80%are sought in a single mill throughput at a strip rate of above 1500feet per minute. The rolling pressures are considerably greatertherefore requiring lubricants to form tougher load-carrying films thanhitherto known. The high degree of heat generating from the fast rollingrates must be dissipated quickly and thus the lubricant must be anequally effective coolant. The roll oil must also be able to removemetal fines from the metal being rolled, otherwise they would mar thefinished surface. Also the metal fines should be easily removed from theoil. If permitted to remain in the oil, they can cause metal surfacedefects in later rolling operations. Moreover, the known roll oils tendto remain on the surface of the metals during the annealing stage,leaving severe stains thereon.

Although a lubricant might overcome all the abovementioned problemsunder ideal conditions, it may still be subject to other deficienciesdue to conditions en countered in everyday practice. One of these is theformation of insoluble salts in hard Water. The additive of thisinvention permits the use of hard water by inice creasing the stabilityof the lubricant emulsion therein. This eliminates the costly step ofreducing the hardness level of such water in those areas wherein softwater is not available naturally.

US. Pat. No. 3,071,544 describes rolling oil emulsions containing anumber of components, including a small amount of an organic acid. Theacid is either liquid or oil soluble or is reacted with other componentsin the formulation to provide oil soluble soaps, such as the soaps ofalkanolamines. US. Pat. No. 3,311,557 describes emulsions for the hotrolling of nonferrous metals which contain a fatty acid, a polyol andethanolamine. The ethanolamine reacts with the acid in suflicientproportion to provide a ratio of base number to acid number of from 0.15to 0.4. Specific examples of this patent show the use of oil-soluble,liquid fatty acids.

U.S. Pat. 3,432,434 teaches a metal rolling lubricant containing analkylaromatic hydrocarbon which might contain an alkali or alkalineearth metal phosphate or an amine phosphate.

U.S. Pat. 3,523,895 discloses a lubricant composition closelyparalleling the composition of this disclosure. However, there is nodisclosure or suggestion of the improvement attainable from the use ofthe specific phosphate of this invention.

SUMMARY OF THE INVENTION This invention provides an emulsifiablelubricant comprising an oil from the group which includes paraflinic andnaphthenic mineral oils, synthetic ester lubricants, polyolefin fluidsand polyoxyalkylene oxide fluids, a solid aliphatic monocarboxylic acidand an amount suflicient to improve the hard water stability thereof ofa mixture of monooleyl and dioleyl phosphates.

DESCRIPTION OF SPECIFIC EMBODIMENTS The lubricant emulsions used in thecold rolling of metal in accordance with this invention broadly consistsof about 0.75% to 10% by weight of an oil-solid acid composition inwater. The mixed oil-acid neat composition contains from about 20% toabout 50%, preferably from about 20% to 40%, by weight of the solidacid. The oil-soluble phase, being about to about 50% by weight of theoil-acid composition, includes an oil, such as a mineral oil, i.e.parafiinic or naphthenic oils, emulsifiers and emulsion stabilizers. Theoil may constitute from about 20% to about 60% by weight of the neatcomposition.

When the oil-acid composition is mixed with the water, the oil-solublecomponents become emulsified in the water and the solid acid remains assolid particles adhered to the emulsified oil droplets. Hence thetypical final lubricant emulsion of this invention consists of water,emulsified oil droplets, and the solid acid closely attached to thedroplets.

With regard to the oil-soluble phase, the components include from about1% to about 15% by weight of the oil phase of an alkanolamine havingfrom about 2 to about 4 carbon atoms per alkanol group and from about 1%to about 15% by weight of the oil phase of an emulsifier preferablyhaving a hydrophilic-lipophilic balance of at least 10. In addition tothese two components, the oil phase may also contain from about 0.05% toabout 2% by weight of an aromatic sulfonate and from about 2% to about15% by weight of a monoor dioleyl phosphate ester.

In the most preferred form, the oil-acid composition contains thecomponents in the following percentages: (1) from about 30% to about 50%by weight of a lubricating oil; (2) from about 20% to about 40% byweight of the solid aliphatic saturated mono-carboxylic acid having fromabout 14 to about 26 carbon atoms; (3) from about 3% to about 12% byweight of an alkanolamine having from 2 to about 4 carbon atoms; (4)from about 5% to about by weight of a mixture of monoand dioleylphosphate ester; (5) about 3% to about 12% by weight of an emulsifierhaving a hydrophilic-lipophilic balance of at least 10; and (6) fromabout 0.1% to about 1.5% by weight of an aromatic sulfonate.

It has been found that by using the components of the lubricantcomposition as a 0.75% to 10% emulsion there is provided a surprisinglyeffective lubricant-coolant which overcomes the arduous requirementsencountered in the high speed cold-rolling of metals, such as steel.Mill speeds of greater than 1500 feet per minute, and even higher than2000 feet per minute, with final gauge sizes of as low as 0.0075 inchhave been attained with the use of the lubricants of this invention.

The mixing equipment needed for combining the components of thisinvention are of a conventional nature, known in the art. Preferably theoil, the water, the acid and the other components, with the exception ofcomponent (6), are mixed together initially at a temperature of from 50C. to about 100 C., and preferably 80 to 90 C., for a sufiicient periodto obtain a uniform composition. From about 30 minutes to about 7 hours,preferably 1 hour, of mechanical mixing is ordinarily sufficient toobtain the desired emulsion mixture. It may be found necessary tosubject the mixture to a particle size reduction step in order to obtainuniformity. Such a step may be carried out by means of suitableequipment for this purpose, such as a colloid mill, homogenizer and thelike. The preferred mixing procedure is performed by first using amechanical mixer and then the homogenizer maintaining the temperaturehigher than 60 C., preferably from about 80 to about 90 C. The mixtureis cooled rapidly to a temperature below 50 C., and the aromaticsulfonate is mixed in. The mixture is thereafter submitted to a finalhomogenizing treatment.

Often mixing equipment is not readily available at the mill and,moreover, too much time may be spent at the mill in forming the emulsionlubricant. For the purpose of convenience and the saving of time andexpense, a concentrated emulsion may be initially prepared by thesupplier prior to shipment to the mill. For the best emulsionconcentrate, that is, the compositions which will require the leastmixing time in the mill equipment, compositions containing from about toabout 60% by weight of the above components (1) to (6) and from about80% to about 40% by weight of water are preferred. These concentratesare simply diluted in further amounts of water to produce the 0.75% to10% emulsion for use.

The various individual components of the water-free or neat compositionare discussed hereinafter. The formulations set forth overcome thedisadvantages of some prior art compositions, i.e. they improve thebrightness and cleanliness of cold roll steels, both in the operationand following annealing. They also improve the hard water stability ofsuch formulations.

The oils used in this invention include both naphthenic and paraflinicmineral oils having a Saybolt viscosity in the range of from about 40 toabout 500 S.U.S., preferably cfrom about 60 to about 300 S.U.S. at 100F. and synthetic lubricants, such as synthetic ester lubricants,polyolefin fluids, alkylene oxide-derived fluids and the like having thesame broad and preferred viscosity ranges. The oil is present in amountsranging from about 20% to 60% by weight of the neat composition, andpreferably from about 30% to about 50%.

From about 20% to about 50% by weight of neat composition is analiphatic, saturated monocarboxylic acid having from about 10 to about30, and preferably from about 14 to 28, carbon atoms. This rangeincludes myristic, palmitic, stearic, arachidic, and behenic acids whichare all normally solid, and insoluble in mineral oils and water.Preferably, stearic acid is employed. At elevated mixing temperatures adat mill operating temperatures these acids may become liquefied.However, at reservoir temperatures, it is believed that although theemulsions are stable, a heterogeneous system may result. It is thereforewithin the scope of this invention to use acids which may be in a solidand undissolved state, such as a large particle or suspensoid, at anypoint during the use or storage of the emulsion lubricant.

The alkanolamine is used as an emulsifying agent in the lubricant, inamounts ranging from about 1% to 15% and preferably 3% to 12% by weightof neat composition. Primary, secondary, and tertiary alkanolamines maybe used. Triethanolamine, isopropanolamine, tri-isopropanolamine, andisobutanolamine are examples of suitable compounds for use in thisinvention.

The phosphate used in the practice of this invention is a mixture ofmonoand dioleyl phosphates, wherein the concentration of each componentis within well defined limits. The concentration of mono-oleyl phosphatewill range between about 30 and about 45% of the phosphate mixture, andthe concentration of dioleyl phosphate [C O P(O) OH] will constitute theremainder, i.e., from about 70 to about 55% of the mixture. Thephosphates may be prepared in known ways. For example, the monoanddioleyl phosphates can be made separately by reacting oleyl alcohol andPOCl in the usual ratio, followed by forming the acid. The individuallymade components can then be combined to form the mixture of theinvention. In addition, the mixed monoand dioleyl phosphates can be madein one step by reacting oleyl alcohol with P 0 usually in the ratio of 3moles of alcohol to 1 mole of P 0 It will be understood by those skilledin this art that of oleyl alcohol, as commercially obtainable, is notpure C So, the preferred oleyl alcohol, even one prime commercial grade,is not made up wholly of C18 but is about 60% of unsaturated C withlesser amounts of C C C and C alcohols, which may only be partiallyunsaturated. Some stearyl alcohol may also be present.

The concentration of the emulsifiers or emulsion stabilizers, preferablyhaving a hydrophilic-lipophilic balance of at least 10 or higher, mayrange from about 1% to about 15% and preferably from about 3% to about12% by weight. Included in this category of emulsifiers are cationic,anionic and nonionic emulsifiers, such as amines having from 4 to 36carbon atoms and the C.;C alkyl phenols, and fatty or resin alcohols,fatty acids, esters and partial esters of fatty acids and polyols andfatty acid amides, each having from 4, and preferably from 8, to 36carbon atoms. A preferred group of emulsifiers are the alkoxylatedderivatives of the above-listed organic compounds obtained by reactingthem with an alkylene oxide having from about 2 to 4 carbon atoms, suchas ethylene oxide (also termed ETO). A preferred group of emulsifiers isthe N-acyl-substituted dialkanolamides, the acyl group having 8 to 30carbon atoms, such as lauroyl diethanolamide. Other emulsifiers includegum arabic, often used in the preparation of wax emulsions.

The aromatic sulfonate acts as a control agent of the particle size andviscosity of the emulsion. It is present in relatively minor proportion,ranging from 0.05% to 2.0%, and preferably 0.1% to about 1.5%, by weightof the emulsion concentrate. The aromatic sulfonates include oil solublemetal salts of petroleum sulfonic acids and synthetic alkaryl sulfonicacids, particularly those having a molecular weight of from about 300 to800. The preferred alkyl substituents on the aromatic ring contain fromabout 8 to 24 carbon atoms. The aromatic sulfonate used in thelubricants of this invention is an oil-soluble beta-naphthalene sulfonicacid-aldehyde condensate, and particularly useful is the formaldehydecondensate. Preparations for producing such condensates are generallyknown in the art. They may also be used in the form of an alkali metalsalt.

In connection with the use of the lubricants of this invention, emulsioncompositions containing additionally a liquid fatty acid, having fromabout 12 to about 22 carbon atoms, preferably oleic acid or linoleicacid, in combination with an aliphatic fatty acid amide having fromabout to about 18 carbon atoms, preferably lauroyl amide, possessfurther improved anti-corrosion properties in the cold-rolling of steel.Oleic acid offers additional oiliness characteristics which aid in thefilmforming properties of the lubricant, but it does not provide anyanti-corrosion protection by itself. It is known that amides do providesome anti-corrosion properties alone. However, in the presence of oleicacid, the fatty acid amide acts in an improved manner evidencing unusualcooperation, as between coagents. The combination of oleic acid andlauroyl amide protects the surface of the metal strip against rust in avery effective manner. The oleic acid is used in minor quantitiesranging from 1% to about 5% by Weight of concentrate. The amide is usedin amounts ranging from about 4% to about 8% by weight of concentrate.

As indicated heretofore, the compositions. of this invention areparticularly useful in the cold-rolling of steel, as well as in othermetalworking operations. The lubricants herein described permit the highspeed gauge reduction of the metal in metal rolling operations. Theyalso provide an unusual improvement in removing metal fines caused inthe rolling. It is well known that in rolling of metal when the metalbillet is fed into rollers, small particles of metal may break off.These particles usually remain in the lubricant. When normal lubricantsare used, the smaller particles, or fines, do not always settle out whenthe lubricant is passed into the reservoir or holding tank at theconclusion of the rolling operation. Hence, when the lubricant is usedagain, these fines may be carried onto the metal surface in thesucceeding rolling operation and cause surface blemishes. While it istrue that the used lubricant is skimmed in the holding tank, it has beenfound that skimming does not always remove all of the metal fines, andthe finished metal strip may be marred. The performance of the emulsionlubricants of this invention is unique in that the presence of the solidacid may act to reject the metal fines from the emulsion and float themto the surface where they are removed in the skimming step.

The following examples show how the hereindisclosed lubricants areimproved with respect to hard water stability by using the mixedphosphate esters of the invention.

Naphthenic oil havin%a viscosity of 100 S.U.S. at 100 F.

Solvent refined para nic oil having 8. 71500811237 of 100 S.U.S. at 100F.

Hydrogenated tallow fatty acids having the COmDOSI'tIOD (wt. percent):13% C14; 23-33% C10; and 6577% C15.

All the components, except for the sulfonate-formaldehyde condensate,were combined under agitation with sutficient water to provide the 30%emulsion. The mixing was performed for about 1 hour, at about to C. Themixture was then passed through a Manton-Gaulin homogenizer for anadditional hour. The resulting emulsion was cooled and the condensatewas added over a half-hour period, with agitation, at a temperaturebelow 50 C. The cooled mixture was again passed through the homogenizer,while maintaining the temperature be low 50 C., for 1 hour.

The above emulsion was stored for one month at ambient temperatures. Atthe end of that time, solids separation on dilution was measured bycentrifuging. A sample diluted to 3% in ASTM hard water (345 p.p.m.) andcentrifuged 10 minutes gave 15 ml. of solids.

EXAMPLE 2 A formulation like that of Example 1 was prepared, with thefollowing exceptions:

(a) 1.0 part of lauroyl diethanolamide instead of 2.0

parts;

(b) 2.0 parts of a mixture of about 40% of monooleyl phosphate and about60% of dioleyl phosphate in place of the tricresyl phosphate; and

(c) 69.85 parts of water instead of 68.85 parts.

After storing for one month at ambient temperatures, this emulsion gavethe following results regarding stability in water. A sample diluted to3% in the ASTM hard water of Example 1, when centrifuged for 10 minutesgave 6 ml. of solids.

It can be seen. from the results shown in Examples 1 and 2 that theaddition of the oleyl phosphate esters of this invention gives asignificant reduction in the solids obtained in hard water. Thus, at a3% concentration in hard water, the mixed phosphate of this inventionaffords a reduction of 9 ml. of solids (from 15 ml. to 6 ml.). It shouldbe noted also that the specific phosphates of this inventionsignificantly reduce the amount of solids obtainable in distilled water.In this connection, 5% of the Example 1 composition in distilled watergave 7 ml. of solids after 3 minutes of centrifuging, Whereas a 3%dilution of the Example 2 formulation in distilled water gave only 3 ml.of solids after 10 minutes of centrifuging.

I claim:

1. An emulsifiable lubricating composition suitable for the cold-rollingof metals and having increased hard water stability, said compositionmade by mixing from about 20% to about 60% by weight of a lubricatingoil selected from the group consisting of naphthenic and parafiinicmineral oils, synthetic ester lubricants, polyolefin fluids, andpolyoxyalkylene fluids, from about 20% to about 50% by weight of asaturated solid aliphatic monocarboxylic acid having from 10 to about 30carbon atoms, from about 1% to about 15% by weight of an alkanolaminehaving from 2 to about 4 carbon atoms per alkanol group, from about 1%to about 15% by weight of an emulsifier having a hydrophylic-lipophilicbalance of at least 10, from about 0.05% to about 2.0% by weight of anaromatic sulfonate having a molecular weight between about 300 and 800and from about 2% to about 15 by weight of a phosphate, the improvementwhereby said phosphate is a mixture of from about 30 to about 45% ofmonooleyl phosphate and from about 70 to about 55% of dioleyl phosphate.

2. The composition of claim 1 wherein the mixture of phosphates ispresent to the extent of from about 5 to about 10% by weight.

3. The composition of claim 1 comprising from about 20% to about 40% byweight of acid having from about 10 to about 20 carbon atoms, from about3% to about 12% by weight of alkanolamine, from about 3% to about 12% byweight of the emulsifier, and from about 0.1% to about 1.5% by weight ofaromatic sulfonate.

4. An emulsion lubricant composition comprising from about 0.75% toabout 10% by weight of a composition of claim 3 and from about 99.25% toabout 90% by weight of water.

5. The composition of claim 3 wherein the acid is hydrogenated tallowfatty acid.

6. The composition of claim 3 wherein the alkanolamine istriethanolamine.

7. The composition of claim 3 wherein the emulsifier is lauroyldiethanolamide.

8. The composition of claim 3 wherein the aromatic sulfonate is anaphthalene sulfonate-formaldchyde condensate.

9. The composition of claim 8 wherein the said condensate is in the formof an alkali metal salt thereof.

References Cited UNITED STATES PATENTS 3,523,895 8/1970 Ishibashi et al.25249.5 X 3,496,104 2/1970 Shimada et a1. 25249.5 X 2,291,066 7/1942Waugh 252-495 X PATRICK P. GARVIN, Primary Examiner W. H. CANNON,Assistant Examiner US. Cl. X.R.

